What is the structure of a kidney?

The kidney is a bean-shaped organ composed of an outer cortex, an inner medulla, and a renal pelvis.

The kidney, one of the most vital organs in the human body, is a complex structure with several distinct parts. It is bean-shaped and typically about the size of a fist. The outermost layer of the kidney is known as the renal cortex. This is a light-coloured layer that contains most of the kidney's nephrons, the functional units responsible for filtering blood and producing urine.

Beneath the cortex lies the renal medulla, which is darker and contains the remaining nephrons. The medulla is divided into several cone-shaped sections called renal pyramids. These pyramids point towards the centre of the kidney and their tips, known as papillae, empty into the renal pelvis.

The renal pelvis is a funnel-shaped space in the centre of the kidney. It collects the urine produced by the nephrons and channels it into the ureter, a tube that carries the urine to the bladder for storage until it can be excreted from the body.

Each nephron in the kidney consists of a glomerulus and a renal tubule. The glomerulus is a network of tiny blood vessels where waste products are filtered from the blood. The filtered blood then flows into the renal tubule, where water and electrolytes are reabsorbed back into the bloodstream, and the remaining waste products are converted into urine.

The kidneys also have a rich blood supply, with the renal arteries delivering blood to the kidneys and the renal veins carrying blood away. This blood supply allows the kidneys to perform their vital functions, which include filtering waste products from the blood, regulating blood pressure, and maintaining the body's balance of electrolytes.